Field of the Invention
The invention is directed to pen needles adapted for attachment to a medication delivery device such as a medication pen. The pen needles according to the invention have attachment mechanisms that provide sensory feedback, such as an audible clicking sound or tactile sensation when the needle-bearing hub is fully seated on the medication pen, and other features that enhance ease of use.
Description of the Related Art
Pen needles are used to attach to a medication pen and are especially popular for delivering self-administered injectable medications such as insulin. In one well known commercial device, a needle-bearing hub is provided inside a funnel-shaped outer cover, sometimes referred to as the “outer shield,” or simply as the “cover.” The cannula is affixed in an axial bore of the hub with one end protruding from the distal or “patient side” of the hub, and the other end of the needle is recessed in a cavity on the proximal or “non-patient” side of the hub, adapted for attachment to the medication pen. A paper and foil “teardrop” label is heat sealed on the edge of the open end of the funnel shaped outer cover. In addition, the medication pen may have a cap received over the distal end of the medication pen, over the opening where the pen needle is installed. To install the pen needle on a medication pen, the user removes the medication pen cap. The user then removes the label on the pen needle outer cover and holds the outer cover to install the hub, typically threading the hub onto the pen. Once the hub is installed on the medication pen, the outer cover can be removed by pulling the outer cover distally off the hub. A separate inner needle shield sits over the needle, which the user must remove to administer an injection. The inner shield generally sits on the hub and simply helps the user locate the needle without forming a sterility barrier. After use, the user may use the outer cover to unthread the hub from the pen and dispose of the pen needle.
Medication pens and associated pen needles are disclosed in U.S. Pat. No. 7,645,264, and U.S. Patent Application Publication Nos. 2009/0069755 and 2012/0022460, all of which are incorporated by reference in their entirety for their teaching of pen needle design and construction. A device for releasably arranging a pen needle on an injection pen and releasing the pen needle into a mating storage or disposal container is disclosed in U.S. Pat. No. 8,057,444, also incorporated by reference.
With the prior art described above, it is not always possible for the user to tell that the hub is properly seated on the medication pen. The pen does not provide a sensory feedback that the pen needle is seated on the pen (other than the tightening of the threaded connection itself). This can lead to over-tightening the pen needle on the pen, which would render the pen needle difficult to remove, or under-tightening the pen needle on the pen, which could cause the pen needle to leak. Likewise, when removing the needle, the outer cover does not always align properly over the hub and it may take two or more tries to unscrew the hub. Although passively shielded pens are known, including pens which shield the non-patient end of the needle automatically after use, many pens simply leave the non-patient end of the needle exposed after use, relying on the proximal end cavity to provide protection from accidental needle sticks after use. It would be desirable to have a pen needle which addressed these perceived drawbacks of the prior art.